Sometimes it seems like the most harmless questions, posed out of mild interest or for amusement during these cold rainy days, can manage to stir up some unnecessary heat. I frequently run on parts of my hikes and can come up on people pretty quickly, and, if the trail surface is soft, they may not hear me, so I will always call out a simple "hello", hopefully just loud enough for them to hear me. Once or twice I didn't do this in time and the person really jumped. It never seemed necessary to yell or be very loud about it. I do find loud groups somewhat jarring when I'm in a quiet, peaceful mode, but then I have to tell myself that they're having their own version of a good time, and really it's not long before I can't hear them again.
With regard to bears, from my hiking out west, the general consensus of the locals seems to be that the bear bells don't really work, they're not loud enough to really impact a bear, and they certainly are annoying to listen to. What I heard was that if you are in known bear country and you are coming around a blind turn, or going into thick brush, or some other trail feature where you may startle a bear on the trail, a somewhat loud announcement of your presence could be useful. I have done some mountain biking in areas where there had been some history of bikers getting into nasty encounters with bears they surprised on the trail, so I would try to call out coming around blind turns. I was on a trail run once in Yellowstone and whipped around a bend to come face to face with a large antlered deer, that was startling enough for both of us (he/she turned tail and ran), but a reminder to me that I needed to take care in heavy wildlife areas.
